DrawInterfaceInClass.md

An Interface Activity

The objective of this bonus activity is to help you to understand Java Interfaces and JavaFX concepts.

Introduction

Interfaces are used to enforce some sense of expected behaviour. Classes that implement a specific Interface need to implement the Interface's methods. For example, if we had a Drawer interface with a method draw, we can expect any class that implements this method to implement that draw method. This gives us an idea about what behaviour classes that implement the Drawer interface are capable of doing (capable of drawing something).

Tasks

In this exercise, you will develop your own work of art using JavaFX's GraphicContext class. Have a look at the documentation. You will need to write a 2 classes that implement the Drawer interface, run your classes using the driver below and answer the questions.

    import javafx.scene.canvas.GraphicsContext;
    
    public interface Drawer{
    	public void draw(GraphicsContext gc);
    }

Notice that the interface contains one abstract method that awaits your implementation. Write two seperate classes following this notation: DrawerClass[num] (example: DrawerClass1, DrawerClass2) that implement the draw method of the Drawer interface. One example of how GraphicsContext can be used is the following:

    public void draw(GraphicsContext gc) {
    	gc.setFill(Color.GREEN);
    	gc.setStroke(Color.BLUE);
    	gc.setLineWidth(5);
    	gc.strokeLine(40, 10, 10, 40);
    	gc.fillOval(10, 60, 30, 30);
    	gc.strokeOval(60, 60, 30, 30);
    }

This produces the following work of art:

Notice that colors are set using the setFill() and setStroke() methods. The setLineWidth determines how many pixels the outline of your shape is. Also, methods that start with stroke, like strokeOval() and strokeLine() are used to draw the specified shape. Refer to the documentation for GraphicsContext to see what other shapes you could use.

You will be given a 500x500 pixel Canvas to paint on. Draw your masterpiece. This exercise is due in class and you will be submitting your code by email to the instructor who will demonstrate the use of your written class to produce the output. Add your name and ID to the top of your submitted code as a @author tag.

Instructions to Run your Code

There are two things that you need to do. You must compile all the classes submitted to you by the students using javac *.java. Additionally, you must enter the NUM_OF_GROUPS constant which you will be prompted for when you run java InterfaceDriver. Here is the InterfaceDriver code:

    import javafx.application.Application;
    import javafx.scene.Group;
    import javafx.scene.Scene;
    import javafx.scene.canvas.Canvas;
    import javafx.scene.canvas.GraphicsContext;
    import javafx.stage.Stage;
    import javafx.scene.control.Button;
    import javafx.event.*;
    import java.util.Scanner;
    
    public class InterfaceDriver extends Application {
    	//Modify this based on the number of groups you've assigned to the class
    	private static int NUM_OF_GROUPS;
    	
	    public static void main(String[] args) {
	    		launch(args);
	    }
     
	    @Override
	    public void start(Stage primaryStage) {
	    	System.out.println("Enter the number of groups you've assigned to this section:");
    		Scanner s = new Scanner(System.in);
    		NUM_OF_GROUPS = s.nextInt();
    		
    		primaryStage.setTitle("Drawing Interfaces Driver");
    		Group root = new Group();
    
    		Button b = new Button();
    		b.setText("Generate!");
    		b.setOnAction(new EventHandler<ActionEvent>() {
    			@Override public void handle(ActionEvent e) {
    				for(int i = 1; i <= NUM_OF_GROUPS; i++){
    					Stage stage = new Stage();
    					Group root1 = new Group();
    					Canvas canvas = new Canvas(500, 500);
    					GraphicsContext gc = canvas.getGraphicsContext2D();
    					try{
    						Drawer d = (Drawer) Class.forName("DrawerClass" + i).newInstance();
    						d.draw(gc);
    					}catch(Exception e1){
    						e1.printStackTrace();
    						System.exit(0);
    					}
    					root1.getChildren().add(canvas);
    					stage.setScene(new Scene(root1));
    					stage.show();
    				}
    			}
    		});
    		
    		root.getChildren().add(b);
	    	primaryStage.setScene(new Scene(root));
	    	primaryStage.show();
	    }
    }